Structure Selection And Optimization For Head Cover, Spiral Case And Stay Ring Of 700MW Class Hydro Turbine

Head cover,spiral case and stay ring are important components of hydro power unit,which work under huge water pressure.The safe and stable operation of unit is to some extent determined by the stiffness and strength characteristics of head cover,spiral case and stay ring.The establish of large hydro power unit can bring some benefits,such as reducing the number of units,saving the project investment and saving operating cost of power station.The capacity of hydro power unit represents the level of design and manufacture of unit,so it is necessary to pay more attention to the structure optimization of head cover,spiral case and stay ring.Structure model selection and structure optimization are implemented to head cover,spiral case and stay ring of large hydro turbine by using finite element method in this paper.Firstly,the uniform finite element analysis strategy of head cover,spiral case and stay ring are determined,which bring convenience to comparing difference of stiffness and strength characteristics between different structure of head cover,spiral case and stay ring.Secondly,stiffness and strength characteristics of head cover,spiral case and stay ring are compared and analyzed based on the right bank of Three Gorges Dam power station,the left bank of Three Gorges Dam power station,Longtan power station,Nuozhadu power station,Xiaowan power station,Laxiwa power station and Goupitan power station.By comprehensive evaluation of stiffness and strength characteristics of head cover,spiral case and stay ring of large hydro turbine,the main factors influence the stiffness and strength characteristics of head cover,spiral case and stay ring are determined.Upper plate thickness H5 and upper connecting plate thickness H3 could reduce stress by 7%.Spiral case center radius T1,spiral case radius T2 and connecting plate end radius T6 could reduce stress by 14%.Thirdly,in the aspects of topological structure,geometry and thickness configuration of steel plate,the main factors influence the stiffness of head cover of hydro turbine are analyzed,and specific measures for improving the stiffness of head cover are proposed.By analytic calculation,theoretical thickness of spiral case is studied,which is the design basis for subsequent finite element analysis and proper thickness configuration of steel plate of spiral case.By using variable analysis technology,the relationship between stress level and thickness of steel plate and geometry of spiral case is researched.Then,the proper range of steel plate thickness and geometry of spiral case are determined.For normal head cover,internal bottom plate T6,vertical plate T4,external upper plate T7 and long rib T8 could reduce axial displacement by 3%.For upper flange head cover,flange thickness T1 and external upper plate T2 could reduce axial displacement by 8%.Finally,on the basis of structure design of head cover,spiral case and stay ring of Xiluodu hydro turbine,by using variable analysis technology,structure model selection and structure optimization of head cover,spiral case and stay ring are carried out.According to the results of finite element analysis,the effectiveness of the optimizing method is validated.